Spark plug



y 1931. B. A. BIRDSALL I 1 ,805,752

4 SPARK PLUG Filed April 2, 1929 gwtwnbz Patented May l9, 1931' UNITED STATES PATENT OFFICE BERT A. IBIRDSALL, OF DECATUR, NEBRASKA, ASSIGN'OR OF ONE-HALF T HENRY (h KING, OF DECATUR, NEBRASKA SPARK PLUG Application filed April 2,1929. Serial No. 351,958

This invention relates to improvements in spark plugs, particularly spark plugs designed for use in internal combustion engines.

The primary object ofthis invention is to provide a spark plug so designed and constructed that fouling thereof will not take place.

Another object of the invention to provide an improved type of spark plug so constructed that an intensifying of the current will take place through the provision of gaps across which a firing current must jump, means being provided whereby one.of said gaps may be adjusted.

Still another object of the invention is to providean improved spark plug so designed that the expanding and contracting action of the metal of the electrodes, when the same be.-

come hot, will not change the spark gaps to weaken the spark produced.

Other objects and advantages of the invention will become apparent as the description of the same proceeds and the invention will be best understood from a consideration of the following detailed description taken in connection with the accompanying drawing forming a part ofthe present invention with the understanding, however, that the invention is not confined to any strict conformity with the showing of the drawing but may be changed or modified so long as such changes ormodifications mark no material departure from the salient features of the invention as expressed in the appended claim.

In the drawings Figure 1 is a central longitudinal sectional view of the spark plug embodying the present invention;

Figure 2 is an elevational view of the lower end of the plug.

Referring to the drawings in detail wherein like numerals of reference indicate corresponding parts throughout the several views, the numeral 1 indicates'the porcelain body of the present sparkplug, which body as shown, is relatively long and is circumferentially enlarged adjacent the lower end, as indicated at 2, and between the enlargement 2 and the adjacent end is of tapered formation, as indicated at 3.

In the upper end of the body 1 a recess or pocket 4 is formed andadjacent the pocket the body is provided with the surrounding" groove 5 in which the edge of a metal'cap 6; is forced when the cap is placed in position over the top end of the insulation body in the manner shown. The top portion 7 of the cap 6 is provided with a threaded aperture 8 which opens into the recess 4, and this threaded aperture has extended therethrough the electrode screw 9, the upper end of which has a kerf lOformed transversely thereof for the reception of a screw driver when the spark gap, hereinafter described, located in. the recess 4, is tobe adjusted.

Formed to receive the lower portion of the insulation body 1, is a cylindrical shell 11 of the usual type, the lower end of which ,is exteriorly threaded, as indicated at 12 for engagement in the cylinder head of an engine. Intermediate the ends of this-shell the inner face of the wall is provided with a shoulder 13 to receive the lower edge of the enlarged por tion 2 of the insulation body and surrounding the insulation body and threadedly secured in the upper end of this shell is a binding nut insulation body in position.

As is shown, the tapered lower end of the insulation body 1v terminates above the lower end ofthe shell body 11 and the ,inner edge of the shell body is beveled as at 15, so the inner wall of the lower end of the shell flares outwardy, as shown.

Running longitudinally through the insulation body 1 is a main central electrode 16, the upper end of which extends into the recess 4 and is formed to provide the head 17 whichis normally spaced from the lower end of the screw 9 to form a spark gap therewith. The lower end of the electrode 16 extends downwardly beyond. the lower end of the insulation body 1, and'secured in the lowered tapered end of the insulation body'adjacent the electrode 16, is an auxiliary electrode 18. The space between the angled portion of the auxiliary plug 18 and the beveled face 15 of the shell is adjusted to 've a spark-of the best character and due to t e re I lation between the angled tportion of the auxiliary electrode and the eveled portlon of the shell this space will not vary with the ex ansion and contraction of theelectrode.

Having thus described my invention, what 7 I claim is v A spark plug, comprising a shell having an inner edge atone end beveled, an insulation body secured in the shell with one end adjacent said beveled edge, a main electrode ex-- tending through said body and projecting straight from said end, and an auxiliary electrode extending from said end of the body and having one portion angled to parallel the face of said bevel and a terminal portion extending transversely of and spaced from the adjacent straight portion of the main dectrode.

In testimony whereof I hereunto aflix my s1gnature.-

- BERT A. BIRDSALL.

e auxiliary electrode 18 in addition to 

